Coupling



FIG. 1 is a perspective view of a coupling showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof, the left side elevational view being a mirror image thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a top plan view thereof. 

The ornamental design for a coupling, as shown and described. 